[0001] The present invention relates to an ink jet recording head and a method of producing
same.
[0002] There are two types of ink jet recording heads, i.e., the piezoelectric vibration
type in which ink is pressurized by mechanically deforming a pressure chamber, and
the bubble jet type in which a heating element is disposed in a pressure chanter and
ink is pressurized by an air bubble produced by heat of the heating element. Ink jet
recording heads of the piezoelectric vibration type are classified into two categories,
a first recording head using a piezoelectric vibrator which is axially deformed, and
a second recording head using a piezoelectric vibrator which conducts flexural displacement.
The first recording head can be driven at a high speed and performs recording at a
high density, but requires a cutting operation for producing the piezoelectric vibrator,
and a three-dimensional assembly operation for fixing the piezoelectric vibrator to
the pressure chamber, thereby producing a problem in that an increased number of production
steps are necessary. By contrast, in the second recording head, the piezoelectric
vibrator has a membrane-like shape, and hence can be formed by baking the piezoelectric
vibrator integrally with an elastic film constituting the pressure chamber. Consequently,
the second recording head has a reduced number of production steps. However, the second
recording head requires an area of a size sufficient to conduct flexural vibration
so that the pressure chamber has a large width, thereby reducing the arrangement density.
[0003] In order to solve the problem of a recording head using flexural vibration, for example,
Japanese Patent Publication (Kokai) No. HEI5-504740 discloses an ink jet recording
head comprising: a substrate in which pressure chambers are formed in a single-crystal
silicon substrate of a (110) lattice plane; and a nozzle plate in which a plurality
of nozzle openings communicating with the pressure chambers are formed and which is
fixed to one face of the substrate. The other face of the substrate is formed as a
membrane which is elastically deformable. A driving portion is integrally disposed
by forming a piezoelectric film on the surface of the membrane by a film formation
method. The driving portion conducts flexural vibration so as to pressurize ink in
the pressure chambers, thereby ejecting ink drops from the nozzle openings.
[0004] In the disclosed head, the pressure chambers, ink supply ports attached to the chambers,
and a reservoir are formed by conducting anisotropic etching on a single-crystal silicon
wafer. Because of the characteristics of anisotropic etching, the pressure chambers
are obliged to be arranged along a 〈111〉 lattice orientation of the single-crystal
silicon wafer. This causes the wall face of the reservoir for supplying ink to the
pressure chambers, to be formed on a (110) plane which is perpendicular to the 〈111〉
lattice orientation. However, it is very difficult to form the (110) plane by conducting
anisotropic etching on a single-crystal silicon substrate. Therefore, a technique
in which a wall face defining a reservoir is etched so as to be approximated by a
continuum of minute (111) planes is employed.
[0005] In order to form minute (111) etched planes, patterns which are called compensating
patterns and disclosed in, for example, Japanese Patent Publication (Kokai) No. HEI7-125198,
must be formed so as to prevent the etching from being excessively conducted. The
compensating patterns are gradually shortened as the etching of a single-crystal silicon
wafer proceeds, and then formed into a sword-like shape which is necessary for minute
(111) planes to remain at the completion of the etching. Consequently, the ink reservoir
must have a width which is greater than at least the length of the compensating patterns,
so that extra regions for the compensating patterns are required. This produces problems
in that the size of the ink jet head is increased, and that an expensive wafer is
wastefully consumed.
[0006] When an image such as a graphic image is to be printed, since dots must be formed
at a high density, nozzle openings also are required to be arranged at a high density.
As a result, very small ink drops, in the order of 10-30 ng per drop, are required
to be ejected. In order to comply with these requirements, improvements such as reduced
width pressure chambers, and partition walls of the pressure chambers having a reduced
thickness must be produced in the substrate in which flow paths are to be formed.
When the width of the fluid pressure chambers is reduced or when the partition walls
are made thin, however, there arise further problems in that the ink flow in the pressure
chambers is impeded, that air bubbles remain in the flow paths, and that the partition
walls are easily deflected and crosstalk occurs, thereby impairing the printing quality.
[0007] Even when such requirements are fulfilled, a further requirement is produced as described
below. A nozzle plate which closes one face of each pressure chamber is elastically
contacted with and sealed by a capping member for preventing the flow paths from clogging,
and rubbed with a cleaning member which is made of an elastic material such as rubber.
Consequently, the nozzle plate must have a mechanical strength which can endure such
operations. In order to ensure the strength, a metal plate member constituting the
nozzle plate must have a thickness of 80 µm or more. On the other hand, nozzle openings
which can eject ink drops satisfying the above-mentioned requirements have a diameter
of about 30 µm on the ink ejection side. In the view point of problems which may be
produced in processing, the diameter of nozzle openings on the pressure chamber side
must be at least 70 µm, preferably about 90 µm. When pressure chambers are designed
so as to have a reduced width so as to attain a higher arrangement density, therefore,
nozzle openings are partly closed by partition walls of the pressure chambers, thereby
producing a problem in that ink flow from the pressure chambers toward the nozzle
openings is impeded.
[0008] Furthermore, a signal must be supplied to the driving portion without impeding the
vibrating operation. Therefore, it is impossible to directly connect a cable to the
driving portion. To comply with this, a structure must be employed in which a lead
pattern elongating to the driving portion is formed on the surface of a vibrating
plate and a cable is connected to the lead pattern at a position which is separated
from the vibrating region. When the driving portion is formed by the above-mentioned
film formation method, the level difference between the driving portion and the lead
pattern must be made as small as possible so as to ensure the connection therebetween.
Therefore, a countermeasure is taken in the following manner. The piezoelectric film
constituting the driving portion is extended to the region where the lead pattern
is to be formed, so as to serve as an insulating film for insulating a lower electrode.
Thereafter, a lead pattern is formed on the surface of the piezoelectric film by vapor
deposition or the like. However, this countermeasure has the following disadvantage.
An electrostatic capacity of a value which is negligible in the view point of transmission
of a signal is produced between upper and lower electrodes in the wiring region. This
occurs because the piezoelectric film has originally a high specific dielectric constant
and is very thin. The extra electrostatic capacity produces problems such as the apparent
power is increased and the driving circuit is required to have a large current capacity,
and that, when a voltage is applied to the lead pattern, piezoelectric displacement
or heat generation is caused although the region is a wiring region, whereby the lead
pattern formed on the surface is broken or the film is stripped.
[0009] The present invention intends to overcome the above problems. This object is solved
by the ink jet recording head according to independent claims 1, 9 and 14 and the
method of producing an ink jet recording head according to independent claims 8, 13
or 15.
[0010] Further advantages, features, aspects and details of the invention are evident from
the dependent claims, the description and the accompanying drawings. The claims are
intended to be understood as a first non-limiting approach of defining the invention
in general terms.
[0011] Generally, the invention relates to an ink jet recording head in which a part of
a pressure chamber communicating with a nozzle opening is expanded and contracted
by an actuator conducting flexural vibration, thereby ejecting ink drops through the
nozzle opening.
[0012] The invention is directed to an ink jet head comprising: a nozzle plate in which
a plurality of nozzle openings are formed; a flow path substrate comprising a reservoir
to which ink is externally supplied, and a plurality of pressure chambers which are
connected to the reservoir via an ink supply port and which respectively communicate
with the nozzle openings; an elastic film which pressurizes ink in the pressure chambers;
and driving means located at a position opposing the respective pressure chamber for
causing the elastic film to conduct flexural deformation, wherein the pressure chambers
are arranged in a single-crystal silicon substrate of a (110) lattice plane and along
a 〈112〉 lattice orientation.
[0013] Therefore, it is a first aspect of the invention to provide an ink jet recording
head using a single-crystal silicon substrate which allows the size of the ink reservoir
to be reduced to a value that enables the printing function.
[0014] Furthermore, the invention is directed to an ink jet head comprising: a nozzle plate
in which a plurality of nozzle openings are formed; a flow path substrate comprising
a reservoir to which ink is externally supplied, and a plurality of pressure chambers
which are connected to the reservoir via an ink supply port and which respectively
communicate with the nozzle openings; an elastic film which pressurizes ink in the
pressure chambers; and driving means located at a position opposing the respective
pressure chamber for causing the elastic film to conduct flexural deformation, wherein
the pressure chambers are arranged in a single-crystal silicon substrate of a (110)
lattice plane and along a 〈112〉 lattice orientation, and a nozzle connecting portion
is formed in a region opposing the nozzle openings, the nozzle connecting portion
being wider than the other region.
[0015] Therefore, it is a second aspect of the invention to provide an ink jet recording
head in which the pressure chambers can be arranged at a high density while preventing
crosstalk from occurring, and the pressure chambers and the nozzle openings are smoothly
joined to each other so that ink drops are stably ejected.
[0016] Furthermore, the invention is directed to an ink jet head comprising: a nozzle plate
in which a plurality of nozzle openings are formed; a flow path substrate comprising
a reservoir to which ink is externally supplied, and a plurality of pressure chambers
which are connected to the reservoir via an ink supply port and which respectively
communicate with the nozzle openings; an elastic film which pressurizes ink in the
pressure chambers; and driving means located at a position opposing the respective
pressure chamber for causing the elastic film to conduct flexural deformation, wherein
the ink jet head further comprises on a surface of the elastic film: a lower electrode;
a piezoelectric film formed in a region opposing the respective pressure chamber;
a second film having a composition different than that of the piezoelectric film formed
in a wiring region for supplying a driving signal to the piezoelectric film, the second
film having a dielectric constant and piezoelectric properties which are lower than
those of the piezoelectric film; an upper electrode formed on a surface of the piezoelectric
film; and a lead pattern which is formed on a surface of the second film and connected
to the upper electrode.
[0017] Therefore, it is a third aspect of the invention to provide an ink jet recording
head in which the capacitance of a wiring region can be made as small as possible
so that the load of a driving circuit is reduced, and the possibility of breakage
in the wiring region can be made as low as possible.
[0018] It is a fourth aspect of the invention to provide a method of producing such a recording
head.
[0019] The invention will be better understood by reference to the following description
of embodiments of the invention taken in conjunction with the accompanying drawings,
wherein:
FIGS. 1 and 2 are an exploded perspective view and a section view showing an embodiment
of the ink jet recording head of the invention, respectively.
FIGS. 3a and 3b are a view showing the structure of a flow path substrate as seen
from the top, and a view showing a section taken along a line a-a of an embodiment
of a recording head configured by using the substrate, respectively.
FIGS. 4a and 4b are views showing sections along a longitudinal direction and a width
direction of a pressure chamber and showing steps of forming the flow path substrate
from a single-crystal silicon substrate, respectively.
FIG. 5 is a graph showing relationships between a relative distance Δx between a side
wall of a driving portion and that of the pressure chamber, and a displacement Y of
an elastic film obtained when the driving portion is driven by the same voltage.
FIG. 6 is a diagram illustrating relative positional relationships between the driving
portion and the pressure chamber, and the dimensions of the pressure chamber.
FIG. 7 is a diagram illustrating the ink flow in the pressure chamber of the recording
head of the embodiment.
FIGS. 8a and 8b are section views showing an embodiment of a structure which connects
the pressure chamber of the flow path substrate to a nozzle opening of a nozzle plate,
and a diagram showing the structure of the flow path substrate as seen from the nozzle
opening, respectively.
FIG. 9 is a view showing a section taken in a longitudinal direction of the pressure
chamber and showing an embodiment of a method of producing the flow path substrate.
FIG. 10 is a section view showing an embodiment of the recording head configured with
the flow path substrate.
FIGS. 11a and 11b are section views respectively taken along a longitudinal direction
and a width direction of a pressure chamber and showing another embodiment of the
recording head of the invention.
FIG. 12 is a view showing sections taken in a width direction of the pressure chamber
and showing a method of producing a substrate constituting the recording head.
FIG. 13 is a view showing the structure of a substrate suitable for forming a piezoelectric
film to be formed on the surface of an elastic film, and a wiring portion.
FIG. 14 is a view showing the structure of a driving portion and a wiring portion
which are configured by using the substrate of FIG. 13.
FIG. 15 is a view showing steps of producing the driving portion and the wiring portion.
FIG. 16 is a view showing another embodiment of a substrate suitable for forming a
piezoelectric film to be formed on the surface of an elastic film, and a wiring portion.
FIG. 17 is a view showing the structure of a driving portion and a wiring portion
which are configured by using the substrate of FIG. 16.
FIG. 18 is a view showing steps of producing the driving portion and the wiring portion.
FIG. 19 is a section view showing an embodiment of a recording head in which the elastic
film is configured independently of the flow path substrate.
[0020] FIGS. 1 and 2 show an embodiment of the invention. The reference numeral 1 designates
an ink pressure chamber substrate which is formed by etching a single-crystal silicon
substrate. The top surface of the substrate is used as an opening face 9. A plurality
of rows or, in the embodiment, two rows of pressure chambers 3, 3, ..., and 4, 4,
... which are arranged in a staggered manner, reservoirs 5 and 6 which supply ink
to the pressure chambers, and ink supply ports 7 and 8 through which the pressure
chambers 3 and 4 communicate with the reservoirs 5 and 6 are formed in such a manner
that a membrane portion 2 is formed on the back face. a nozzle plate 12 is fixed to
the opening face 9. In the nozzle plate, nozzle openings 10 and 11 are formed so as
to communicate with one end of a respective one of the pressure chambers 3 and 4.
Piezoelectric films 13 and 14 (see Fig. 2) formed by a film formation method are disposed
on the back face. The ink pressure chamber substrate 1 and the nozzle plate 12 are
integrally fixed to each other so as to attain the liquid-tightness, and are housed
in a holder 15 having supporting parts 15a and 15b which support the peripheral and
center portions, thereby configuring a recording head. In FIG. 1, 17 designates a
flexible cable through which a driving signal is supplied to the piezoelectric films
13 and 14.
[0021] FIG. 3a is a plan view showing an embodiment of the flow path substrate, and FIG,
3b is a view showing a sectional structure. In the figures, 20 designates a wafer
of a single-crystal silicon substrate which is cut so that the surface is a (110)
lattice plane. In the wafer, ink reservoirs 21, 22, and 23 are formed in the side
and center portions, and pressure chambers 24 and 25 are formed between the ink reservoirs
or in two rows. In each of the rows of the pressure chambers 24 and 25, ink supply
ports 26 and 27 or 28 and 29 for receiving ink from the reservoirs 21 and 23 or 22
and 23 which are positioned at both the sides of the row are formed. Ink introducing
ports 30, 31, and 32 for receiving ink from an external ink tank are opened at ends
of the ink reservoirs 21, 22, and 23.
[0022] Next, a method of producing the flow path substrate will be described with reference
to FIGS. 4a and 4b. A base material 42 is prepared wherein an SiO
2 layer 41 of a thickness of about 1 µm is formed by the thermal oxidation method or
the like on the entire surface of a single-crystal silicon substrate 40 which is cut
so that the surface is (110). The SiO
2 layer 41 serves as an insulating film for a driving portion which will be formed
thereon, and also as an etching protective film for a process of etching the single-crystal
silicon substrate 40. A film of zirconia (Zr) is formed on the surface of the SiO
2 layer 41 by sputtering, and the film is subjected to thermal oxidation, thereby forming
an elastic film 43 which has a thickness of 0.8 µm and is made of zirconium oxide.
The elastic film 43 made of zirconium oxide has a large Young's modulus so that distortion
of a piezoelectric film 44 which will be described later is converted into flexural
displacement at high efficiency. A film of platinum (Pt) of a thickness of about 0.2
µm is formed by sputtering on the surface of the elastic film 43, thereby forming
a lower electrode 45. A film 46 (see FIG. 3b) of a thickness of 1.0 µm is formed by
sputtering or the like of a piezoelectric material such as PZT on the surface of the
lower electrode 45. Thereafter, an upper electrode 47 of aluminum (Al) of a thickness
of 0.2 µm is formed on the surface of the film 46 by sputtering or the like (Step
I).
[0023] The upper electrode 47, the piezoelectric film 46, and the lower electrode 45 are
patterned so as to correspond to the arrangement positions of the pressure chambers
24 and 25, thereby forming a driving portion 50. This patterning is determined so
that the arrangement of the pressure chambers 24 and 25 is directed along a lattice
orientation of a 〈-1-1-2〉 zone axis in which zone planes are a (1-1-1) plane and a
(110) plane, or a 〈112〉 lattice orientation which is equivalent to the orientation
(in the description of embodiments, a crystal lattice is denoted by enclosing indices
by curly brackets, for example, (110), a lattice orientation is denoted by enclosing
indices by angle brackets, for example, 〈110〉, and 1-bar of a unit cell is indicated
as -1).
[0024] As a result of the patterning, the upper electrode 47 is patterned so as to serve
also as lead conductors which are independently taken out in correspondence with the
pressure chambers 24 and 25 and used as portions to be connected with a driving circuit.
In the patterning, it is not essential to form the piezoelectric film 46 as divided
films respectively independently corresponding to the pressure chambers 24 and 25.
When the piezoelectric film 46 is divided into portions which are independently provided
for the respective pressure chambers, however, a large amount of flexural displacement
occurs, as described later. Therefore, the division of the piezoelectric film is preferable.
Since the lower electrode 45 functions as a common electrode, it is preferable not
to divide the lower electrode in the patterning. The patterning may be conducted each
time when one layer is formed (Step II).
[0025] Photoresist layers 48 and 49 are formed so that the arrangement of the pressure chambers
24 and 25 is directed along a lattice orientation of a 〈-1-1-2〉 zone axis in which
zone planes are a (1-1-1) plane and a (110) plane, or a 〈112〉 lattice orientation
which has an equivalent orientation (Step III). The SiO
2 layer 41 is removed by using a hydrofluoric acid buffer solution in which hydrofluoric
acid and ammonium fluoride are mixed in proportions of 1 : 6, so as to pattern a window
51 for anisotropic etching. Thereafter, the photoresist layer 49 for the regions of
the SiO
2 layer where the ink supply ports 26, 27, 28, and 29 are to be formed is subjected
to so-called multiple exposure in which the photoresist layer is again exposed to
light. Half-etching is then conducted for about 5 min. by using the hydrofluoric acid
buffer solution so that the thickness of the SiO
2 layer below the photoresist layer 49 is reduced to about 0.5 µm (Step IV).
[0026] After the resist layers 48 and 49 are removed [away], the base material 42 is immersed
into a 10% by weight solution of potassium hydroxide heated to about 80°C, thereby
executing anisotropic etching. As a result of the anisotropic etching, side walls
24a and 25a (see FIG. 3a) constituting the pressure chambers 24 and 25 appear as a
(1-11) plane which is perpendicular to the (110) lattice plane of the surface of the
single-crystal silicon substrate 40, and the other side walls 24b and 25b (see FIG.
3a) appear as a (-11-1) plane which is equivalent to a (1-11) plane. Longitudinal
side walls 21a, 22a, and 23a defining the reservoirs 21, 22, and 23 appear as a (1-1-1)
plane which is perpendicular to a (110) plane, and the other side walls 21b, 22b,
and 23b appear as a (-111) plane which is equivalent to a (1-1-1) plane. By contrast,
bottom portions 24c and 25c (see FIG. 3a) at a diagonal position of the pressure chambers
24 and 25 appear as a (111) plane inclined at about 35 deg. to a (110) plane, and
the other bottom portions 24d and 25d (see FIG. 3a) appear as a (11-1) plane inclined
at about 35 deg. to a (110) plane (hereinafter, planes of (1-11), (-11-1), (1-1-1),
and (-111) which are perpendicular to a (110) plane are denoted merely by a perpendicular
(111) plane, and a (111) plane and a (11-1) plane which are inclined at about 35 deg.
to a (110) plane are denoted merely by a (111) plane of 35 deg.). At the same time,
the SiO
2 layers 41 and 41' which have functioned as protective films are gradually dissolved
so that a portion of about 0.4 µm is etched away, with the result that the SiO
2 layer 41' in the regions where the ink supply ports 26, 27, and 28 are to be formed
has a thickness of about 0.1 µm and the SiO
2 layer 41 in the other region has a thickness of about 0.6 µm (Step V).
[0027] The base material 42 is immersed into the hydrofluoric acid buffer solution during
a period sufficient for removing the SiO
2 layer of 0.1 µm, for example, about 1 min. so that the SiO
2 layer 41' in the regions where the ink supply ports 26, 27, and 28 are to be formed
is removed away and the SiO
2 layer 41 in the other region remains as a layer 41'' of a thickness of about 0.5
µm (Step VI). The base material 42 is immersed into an about 40% by weight solution
of potassium hydroxide so as to be subjected to anisotropic etching, whereby the regions
of the ink supply ports 26, 27, and 28 are again selectively etched. This makes the
regions thinner so that flow paths having a fluid resistance necessary for an ink
supply port are formed (Step VII). When a plurality of recording heads are formed
in the single base material 42, the base material is divided into individual chips.
Finally, a nozzle plate 53 in which nozzles 52 are opened and which is made of stainless
steel is fixed to the chip by an adhesive agent, thereby competing the recording head
(Step VIII).
[0028] In the above, the embodiment in which a single-crystal silicon wafer wherein the
surface is the (110) plane has been described. It is obvious that, even when a single-crystal
silicon wafer of (-110), (1-10), or (-1-10) is used, a recording head may be obtained
in the same manner as described above.
[0029] As seen from the above description, the pressure chambers are arranged in a row along
a 〈112〉 direction. Therefore, the longitudinal side wall of the reservoir can be formed
as a perpendicular (111) plane and the width of the reservoir can be reduced. Accordingly,
it is possible to configure an ink jet head in which the arrangement density of nozzle
openings is high and the size is reduced. This can reduce the amount of an expensive
single-crystal silicon substrate required for the manufacture of the recording head.
Furthermore, the ink reservoir can be configured by a perpendicular (111) plane. Unlike
a conventional etching system in which compensating patterns must be formed, the wall
surface of the flow path can be smoothly formed so as to allow ink and an air bubble
to flow without a hitch.
[0030] When the piezoelectric film is to be patterned in Step II by etching, or formed in
correspondence with the respective pressure chambers, it is preferable to adjust the
sizes so that the distance between the side wall of each piezoelectric film and the
center of the pressure chamber is shorter than that between the side wall defining
the pressure chamber and the center of the pressure chamber. FIG. 5 is a graph showing
the relationship between a relative distance ΔX (in FIG. 5, the minus sign indicates
a projection) between the side walls of the driving portion 50 and the two side walls
25a and 25b defining the pressure chamber 25, and a displacement Y of the elastic
film obtained when the same voltage is applied to the piezoelectric film.
[0031] In the case where the side walls of the driving portion 50 are projected outside
the pressure chamber 25, the displacement of the driving portion 50 is very small
and do not largely vary depending on the degree of the projection. This is caused
by a phenomenon wherein the piezoelectric film of the driving portion 50 which is
outwardly projected from the pressure chamber 25 constrains the side walls 25a and
25b of the pressure chamber 25 of the elastic film. By contrast, in the case where
the side walls of the driving portion 50 are positioned inside the pressure chamber
24, the displacement is abruptly increased so that, in the embodiment, it is maximum
at a position located on the inner side of the side walls of the pressure chamber
25 by about 5 µm and gradually reduced in a direction towards the center of the pressure
chamber. This is caused by a phenomenon wherein the elastic film is free from the
rigidity of the driving portion 50 so as to be easily deformed. When the side walls
of the driving portion 50 are positioned further inward, the displacement becomes
small because the area of the driving portion 50 is reduced. From the above, it will
be seen that the width of the driving portion 50 is preferably formed so as to be
slightly smaller than that of the pressure chamber 24. However, it is not necessary
for the width to be smaller in the whole of the length of the pressure chamber. If
the driving portion is narrower than only a portion of the pressure chamber, the elastic
film is free from the rigidity of the driving portion 50 and hence the degree of displacement
can be increased in accordance with the relative distance.
[0032] In the embodiment, each of the pressure chambers 25 is provided with the ink supply
ports 28 and 29 formed at both the ends in the axial direction. As shown in FIG. 7,
therefore, ink flows along paths which are respectively directed as indicated by arrows
F from both the ends of the pressure chanter 25 to the center portion where the nozzle
opening 52 is formed. Consequently, stagnation of ink at a corner of a pressure chamber
which may often occur in a recording head wherein ink is supplied to a pressure chamber
through a single ink supply port can be prevented from occurring, and an air bubble
in a pressure chamber can be easily discharged to the outside together with an ink
drop by the ink flow.
[0033] As described above, in an ink jet head, a metal plate of a thickness of about 90
µm is usually used as the nozzle plate 53 in the view point of mechanical strength.
Each nozzle opening 52 formed in the nozzle plate has a smooth conical section shape
in which the diameter ⌀1 (FIG. 6) on the side of the ink ejection face is about 35
µm and the diameter ⌀2 on the side of the pressure chamber is about 80 µm. The nozzle
opening is required to allow ink to smoothly flow and stably eject an ink drop of
an amount which is highly accurate.
[0034] When the driving portion is configured as a film as described above, a high electric
field can be produced by a low voltage. When the film is made thinner, however, stress
of a low degree is produced. In order to obtain certain displacement, therefore, the
flexural rigidity of the elastic film must be lowered. When ink in the pressure chamber
is to be ejected in the form of an ink drop from the nozzle opening, however, the
elastic film 41 must have a rigidity which can endure the pressure of the ink. Consequently,
the rigidity of the elastic film cannot be reduced unnecessarily.
[0035] In order to solve the tradeoff problems, the inventor determined that, when the width
W of a pressure chamber is set to be 40 to 50 µm, the degree of displacement is not
reduced and ink is surely pressurized, thereby enabling an ink drop to be satisfactorily
ejected from the nozzle opening 52. As described above, however, the diameter ⌀2 of
the nozzle opening on the side of the pressure chamber is about 80 µm. Therefore,
partition walls defining the pressure chambers having the width W of 40 to 60 µm partly
close the nozzle opening, thereby producing a problem in that the ink flow directed
toward the nozzle opening is impeded.
[0036] FIGS. 8a and 8b show an embodiment which can solve the problem. In the figures, 55
designates partition walls defining the pressure chambers 24. In each of the pressure
chambers, a nozzle connecting portion 56 is formed by forming recesses 55a so that
an opening of a width greater than the diameter ⌀2 of the nozzle opening 52 is ensured.
When ink is to be supplied only from one side of the pressure chamber 24, the nozzle
opening is disposed on the other side of the pressure chamber. When a wafer of a (110)
plane orientation is used as the single-crystal silicon substrate and the above-described
anisotropic etching is conducted, a (111) plane inclined at about 35 deg. to a (110)
plane appears at both the ends of the pressure chamber 24. As shown in FIG. 9, therefore,
a portion which has an inclined face opposing the nozzle plate 53 at an angle of about
35 deg. and which is surrounded by small angles is produced in the pressure chamber
25. An air bubble entering the ink or produced during the operation of the recording
head easily stagnates in such a small-angle region. An air bubble produced in this
way absorbs the pressure of ink which is pressurized by the driving portion 50, thereby
causing the ink ejection ability to be lowered. When the nozzle connecting portion
56 is to be formed, therefore, consideration is preferably taken so that the nozzle
opening 52 is located as near as possible at a position opposing the inclined face
portion 25a.
[0037] FIG. 10 shows an embodiment of a method of producing the above-described pressure
chamber substrate. A single-crystal silicon substrate 40 which is cut at (110) is
subjected to thermal oxidation, thereby preparing a base material 42 on which an SiO
2 layer 41 of about 1 µm is formed on the entire surface. The driving portion 50 is
formed on the surface of the SiO
2 layer 41 in the same manner as described above with respect to FIG. 4b (Step I).
A photoresist layer is formed and the SiO
2 layer 41 is removed by using a hydrofluoric acid buffer solution in which hydrofluoric
acid and ammonium fluoride are mixed in proportions of 1 : 6, so as to pattern a window
49a for anisotropic etching (Step II). Thereafter, the above-mentioned multiple exposure
is conducted only on the regions of the SiO
2 layer which will serve as the nozzle connecting portion 56 and in which the ink supply
ports 26 are formed. Half-etching is then conducted for about 5 min. by using the
above-mentioned hydrofluoric acid buffer solution so that the thickness of the SiO
2 layer is reduced to about 0.5 µm, thereby forming an SiO
2 layer 41' (Step III). After the resist layer is removed away, the base material 42
is immersed into a 10% by weight solution of potassium hydroxide heated to about 80°C,
thereby executing anisotropic etching. As a result of the etching, also the SiO
2 layers 41 and 41' which have functioned as protective films are gradually dissolved
so that a portion of about 0.4 µm is etched away, with the result that the SiO
2 layer 41' in the regions where the ink supply ports 26, 27, and 28 are to be formed
has a thickness of about 0.1 µm and the SiO
2 layer 41 in the other region has a thickness of about 0.6 µm (Step IV). The base
material 42 is immersed into the hydrofluoric acid buffer solution during a period
sufficient for removing the SiO
2 layer of 0.1 µm, for example, about 1 min. so that the SiO
2 layer 41' in the regions of the SiO
2 layer which opposes the nozzle opening 52 and in which the ink supply port 26 is
to be formed is removed away and an SiO
2 layer 41'' of a thickness of about 0.5 µm remains in the other region (Step V). The
base material 42 is immersed into an about 40% by weight solution of potassium hydroxide
so as to be subjected to anisotropic etching, whereby the region which opposes the
nozzle opening 52 and in which the ink supply port 26 is to be formed are again selectively
etched. This makes the regions thinner so that the nozzle connecting portion 56 and
the ink supply port 26 having a necessary fluid resistance are formed (Step VI).
[0038] FIGS. 11a and 11b show an embodiment of another recording head which can solve the
problems caused by connecting the nozzle opening to the pressure chamber and adjusting
the ink amount of an ink drop. The reference numeral 60 designates a center partition
wall in which one end is fixed to an elastic film 61. The other end of the wall elongates
in a region not opposing the nozzle opening 52 to a position abutting the nozzle plate
53, and is configured in the vicinity of the nozzle opening 52 so as to form a through
hole 62 which allows ink to pass therethrough. According to this configuration, one
pressure chamber 64 which communicates with the one nozzle opening 52 is divided by
the center partition wall 60 into two cells 64a and 64b in communication with each
other, and the nozzle plate 53 is supported by a partition wall 65 defining the pressure
chamber 64 and by a part of the center partition wall 60. The thickness of the center
partition wall 60 is selected to be about 15 µm so that, when the pressure chambers
64 of a length of 2 mm are arranged at a pitch of 141 µm, the cells 64a and 64b divided
by the center partition wall 60 have a width of 46 µm.
[0039] On the other hand, on the surface of the elastic film 61, two driving portions 66
and 67 are formed for each pressure chamber so as to be positioned between the center
partition wall 60 and the partition walls 65 defining the pressure chamber 64. In
the figures, 68 designates an ink supply port through which an ink reservoir 69 is
connected to the pressure chamber 64.
[0040] In the thus configured recording head, when a driving signal is applied to the two
driving portions 66 and 67 of one pressure chamber 64 so that the two cells 64a and
64b simultaneously contract, ink of the first cell 64a and that of the second cell
64b are simultaneously pressurized and an ink drop of an amount proportional to the
flexural amount of the two driving portions 66 and 67 is ejected via the through hole
62 from the nozzle opening 52. When a driving signal is applied only to the driving
portion 67 of the one pressure chamber 64, ink of the one cell 64a is ejected from
the nozzle opening 52. As a result, the amount of ink constituting an ink drop can
be easily adjusted by selectively applying a driving signal to only one of or both
of the two driving portions 66 and 67 of one pressure chamber 64, thereby adjusting
the size of a dot which is to be formed on a recording medium. Furthermore, one pressure
chamber 64 can be set to have a width which is approximately equal to the diameter
of the nozzle opening 52 on the side of the pressure chamber, whereby the problem
of the nozzle opening 52 being closed by the partition wall 65 defining the pressure
chamber 64 can be prevented from arising.
[0041] Next, a method of producing a substrate constituting the recording head will be described
with reference to FIG. 12. a base material 72 is prepared wherein an SiO
2 layer 71 of a thickness of about 1 µm is formed by the thermal oxidation method or
the like on the entire surface of a single-crystal silicon substrate 70 which is cut
so that the surface extends along a (110) crystal axis. An elastic film 73 made of
zirconia (Zr) or platinum is formed by sputtering on the surface of the base material
72. In the same manner as described above, a lower electrode, and a piezoelectric
film made of PZT or the like are formed so that two driving portions 74 and 75 are
formed for each pressure chamber (Step I). A photoresist layer is formed at positions
opposing the partition walls 65 and the center partition wall 60 of the pressure chamber.
The SiO
2 layer 71 is removed by using a hydrofluoric acid buffer solution in which hydrofluoric
acid and ammonium fluoride are mixed in proportions of 1 : 6, so as to pattern a window
for anisotropic etching. Thereafter, the above-mentioned multiple exposure is conducted
only on an SiO
2 layer 71' of a region where the through hole of the center partition wall 60 is to
be formed. Half-etching is then conducted for about 5 min. by using the above-mentioned
hydrofluoric acid buffer solution so that the SiO
2 layer 71' of a thickness of about 0.5 µm is formed (Step II). After the resist layer
is removed away, the base material 72 is immersed into a 10% by weight solution of
potassium hydroxide heated to about 80°C, thereby executing anisotropic etching. As
a result of the etching, also the SiO
2 layers 71 and 71' which have functioned as protective films are gradually dissolved
so that a portion of about 0.4 µm is etched away, with the result that the SiO
2 layer 71' in the regions where the through hole of the center partition wall 60 is
to be formed has a thickness of about 0.1 µm and the SiO
2 layer 71 in the other region has a thickness of about 0.6 µm (Step III).
[0042] The base material 72 is immersed into the hydrofluoric acid buffer solution for,
for example, about 1 min. so that the SiO
2 layer 71' in the region where the through hole of the center partition wall 60 is
to be formed is removed away and an SiO
2 layer 71'' of a thickness of about 0.5 µm remains in the other region. The base material
is again immersed into an about 40% weight solution of potassium hydroxide so as to
be subjected to anisotropic etching, whereby a step 60a functioning as the through
hole 62 is formed in the center partition wall 60 (Step IV). The SiO
2 layer 71 in the region of the elastic film 73 opposing the pressure chamber is etched
away by using hydrogen fluoride. Finally, a low-rigidity material such as gold or
aluminum is sputtered onto the surfaces of the driving portions 74 and 75 so that
an upper electrode 76 is formed (Step V). When the elastic film 73 is made of a metal
such as platinum, the elastic film may function as the lower electrode.
[0043] The driving portions which are formed on the elastic film as described above are
configured by using a film forming technique in which a piezoelectric material is
sputtered. Therefore, the driving portions are much thinner than those which are formed
by applying a green sheet of a piezoelectric material, with the result that the driving
portions have a large electrostatic capacity. This produces various problems. Furthermore,
since the piezoelectric material existing in the wiring region has piezoelectric properties
in the same manner as the driving portions, also the wiring region is displaced, thereby
producing a further problem in that the lead pattern formed above is fatigued.
[0044] FIG. 13 shows an embodiment which can solve such problems. In the figure, 80 designates
a flow path substrate which is configured by a single-crystal silicon substrate. In
the same manner as described above, an SiO
2 film 81 and an elastic film 82 which is made of an anticorrosion noble metal or zirconia
oxide are formed on the surface of the substrate. When zirconia oxide is used, a lower
electrode is formed on the surface of elastic film and a piezoelectric film 83 is
then formed so as to cover the entire surface. The piezoelectric film 83 is formed
by subjecting a material such as a PZT material which conducts flexural vibration
in response to an application of an electric field, to a film forming technique, for
example, the sputtering method or the sol-gel method. The reference numeral 84 designates
a low-dielectric constant region having piezoelectric properties and a dielectric
constant which are lower than those of the piezoelectric film 83. The low-dielectric
constant region is formed in a wiring region where a lead pattern for supplying a
signal to the driving portion is disposed. After the piezoelectric film 83 and the
low-dielectric constant region 84 are formed in this way, as shown in FIG. 14, etching
or the like is conducted so that only the regions of the piezoelectric film 83 opposing
the pressure chambers remain and the low-dielectric constant region 84 has a shape
suitable for the formation of the lead pattern, thereby configuring driving portions
85 and lead pattern forming portions 86.
[0045] Next, a production method will be described with reference to FIG. 15.
[0046] A film of platinum which will function as a lower electrode 92 is formed so as to
have a thickness of 800 nm on the surface of an etching protective film 91 of a single-crystal
silicon substrate 90 by a thin-film formation method such as the sputtering film formation
method. In this film formation, in order to enhance the adhesion strength exerted
between the platinum layer and the upper and lower layers, a very-thin intermediate
layer of titanium or chromium may be farmed. In the embodiment, the lower electrode
92 serves also as an elastic film. a film of a first piezoelectric film precursor
93 is formed on the lower electrode. In the embodiment, the film formation was conducted
by the sol-gel method by using a PZT piezoelectric film precursor material in which
lead titanate and lead zirconate are mixed at a mole compounding ratio of 55% and
45%, and repeating steps of applying, drying, and degreasing six times so as to obtain
a thickness of 1 µm.
[0047] It was confirmed that, when the composition is selected so that a resulting piezoelectric
film has the composition of
Pb
CTi
AZr
BO
3
(where A, B, and C are numerals,
, 0.5 ≤ A ≤ 0.6, and 0.85 ≤ C ≤ 1.10),
the precursor can exhibit piezoelectric properties suitable for ejection of ink drops.
It is a matter of course that the film may be formed in a similar manner by using
another film forming technique such as the high-frequency sputtering film formation,
or the CVD. In order to form a low-dielectric constant layer on the surface of the
precursor 93, in the embodiment, a lead oxide film 94 of a thickness of 500 nm is
formed by the sol-gel method (Step I).
[0048] Next, the lead oxide film 94 other than the region which will function as a wiring
region 95 is etched away. Thereafter, the whole of the substrate is heated in an oxygen
ambient at 650°C for 3 min. and then at 900°C for 1 min. The substrate is naturally
cooled so that the first piezoelectric film precursor 93 is crystallized to be completed
as a piezoelectric film 96.
[0049] On the other hand, in the wiring region where the lead oxide film 94 is formed, the
lead of the lead oxide film 94 is caused by the above-mentioned heating to be diffused
and dissolved into the first piezoelectric film precursor 93, with the result that
a different composition film 97 having a low dielectric constant is baked. Analyzation
of the different composition film 97 showed that lead was increased to an amount which
is 1.12 times the total number of moles of zirconia and titanium (Step II). A film
of platinum of a thickness of 200 nm is formed by sputtering on the surfaces of the
piezoelectric film 96 and the different composition film 97, thereby forming an upper
electrode 98 (Step III). The upper electrode 97 and the piezoelectric film 95 are
divided into a predetermined shape by ion milling using an etching mask so as to correspond
to the positions where the pressure chambers are to be formed (Step IV). The etching
protective film 91 on the opposite face of the single-crystal silicon substrate 90
is removed away by hydrogen fluoride so as to coincide of the shapes of the pressure
chamber, a reservoir, and an ink supply port, thereby forming a window 99 (Step V).
The single-crystal silicon substrate 90 is subjected to anisotropic etching using
an anisotropic etchant, for example, an approximately 17% by weight aqueous solution
of potassium hydroxide heated to 80°C, so that the etched portion reaches the protective
film 91 on the surface. Thereafter, the protective film 91 on the back face of the
piezoelectric film 95 is removed by hydrogen fluoride and a flow path of a pressure
chamber 100, etc. is formed (Step VI).
[0050] The thus formed driving portion has an electrostatic capacity of 7 nF per element.
As compared with an electrostatic capacity of about 10 nF obtained in the prior art,
the electrostatic capacity is reduced by about 30%. Reliability evaluation tests by
means of long term printing were performed. In prior art recording heads, at 50,000,000
ink drop ejections, a lead pattern was broken or a film separation occurred so that
a signal supply was disabled. By contrast, in recording heads according to the invention,
the defective rate was reduced or about 1% or less even at 2,000,000,000 ink ejections.
This was caused by the fact that the amount of lead in the different composition film
96 in the wiring region is larger than that in the piezoelectric film 95 so that the
composition is deviated from the optimum composition of a piezoelectric film. The
dielectric constants and piezoelectric properties of the piezoelectric film 95 and
the different composition film 96 were measured. The measurement results show that
the piezoelectric film 95 and the different composition film 96 have dielectric constants
of 1,800 and 900, respectively, and piezoelectric properties of 150 PC/N and 80 PC/N,
respectively. It was confirmed that, according to the invention, both the electrostatic
capacity of one element and the piezoelectric displacement of the wiring region are
reduced and the mechanical fatigue and the fatigue due to a heat cycle in a lead pattern
are decreased.
[0051] The inventor conducted further experiments to investigate piezoelectric properties.
In the experiments, the lead oxide film 94 to be formed on the surface of the PZT
precursor 93 was baked with various thicknesses for the lead oxide film so that the
content of lead oxide with respect to the stoichiometrical composition of the different
composition film 96 was varied. It was found that, when a composition is attained
in which the amount of lead oxide with respect to the stoichiometrical composition
is 0.85 or smaller or 1.10 or larger, piezoelectric properties are largely lowered.
Piezoelectric properties were similarly evaluated by using titanium oxide or zirconium
oxide in place of lead oxide. It was found also that, when the ratio of Ti or Zr to
the total amount of Ti or Zr constituting the piezoelectric film 95 is 0.5 or smaller
or 0.6 or larger, piezoelectric properties are largely lowered. From the above, it
was found that the dielectric constant and piezoelectric properties can be lowered
only by shifting the content of a component element without changing the composition
of the piezoelectric film precursor 93 of the wiring region from that at which the
precursor is expected to operate as a piezoelectric film in an optimum manner.
[0052] In the above, the embodiment in which the elastic film is made of a PZT material
has been described. It is obvious that, even when a material to which another metal
oxide such as nickel niobate, nickel oxide, or magnesium oxide is added, or a material
other than a PZT material is used, the same effects can be attained by adding a material
which ensures the adhesion to a substrate and lowers piezoelectric properties and
the dielectric constant.
[0053] FIGS. 16 and 17 show a further embodiment in which the displacement and the electrostatic
capacity of a piezoelectric film in a wiring region can be reduced. In the embodiment,
a low-dielectric constant layer 111 is formed in a wiring region in the surface of
a piezoelectric film 110 which is formed of the entire surface of an elastic plate
82. After the piezoelectric film 110 and the dielectric layer 111 are formed as described
above, as shown in FIG. 17, etching or the like is conducted so that only the regions
of the piezoelectric film 110 opposing the pressure chambers remain and the low-dielectric
constant layer 111 has a shape suitable for the formation of the lead pattern, thereby
configuring driving portions 112 and lead pattern forming portions 113.
[0054] Next, a production method will be described with reference to FIG. 18. A film of
platinum which will function as a lower driving electrode 92 is formed so as to have
a thickness of 800 nm on the surface of the etching protective film 91 of the single-crystal
silicon substrate 90 on the side of a piezoelectric layer, by a thin-film formation
method such as a sputtering film formation method. A film of a first piezoelectric
film precursor 114 is formed on the lower driving electrode 92. In the embodiment,
the film formation was conducted by the sol-gel method by using a PZT-PMN piezoelectric
film precursor material in which lead titanate, lead zirconate, and magnesium-lead
niobate are mixed at a mole compounding ratio of 55%, 40%, and 10%, and repeating
steps of applying, drying, and degreasing six times so as to obtain a thickness of
1 µm.
[0055] It was confirmed that, when the composition is selected so that the precursor 114
obtained after baking has the composition of
PbTi
AZr
B(Mg
1/3Nb
2/3)
CO
3+ePbO
(where A, B, C, and e are numerals,
, 0.35 ≤ A ≤ 0.55, 0.25 ≤ B ≤ 0.55, 0.1 ≤ C ≤ 0.4, and 0 ≤ e ≤ 0.3), the precursor
114 can exhibit piezoelectric properties suitable for ejection of ink drops. A titanium
layer 115 which has a thickness of 50 nm and will function as the low-dielectric constant
layer 111 is formed by sputtering on the surface of the precursor 124.
[0056] Next, the titanium layer 115 other than the region which will function as a wiring
region 116 is etched away. Thereafter, the whole of the substrate is heated in an
oxygen ambient at 650°C for 3 min. and then at 900°C for 1 min. The substrate is naturally
cooled so that the precursor 114 is crystallized to be completed as a piezoelectric
film. On the other hand, the titanium layer 115 becomes as titanium oxide of a thickness
of about 100 nm so as to form the low-dielectric constant layer (Step II). A film
of platinum of a thickness of 200 nm is formed by sputtering on the surfaces of the
piezoelectric film 117 and the titanium oxide film 118, thereby forming an upper electrode
119 (Step III). The upper electrode 119 and the piezoelectric film 117 are divided
into a predetermined shape by ion milling so as to correspond to the positions where
the pressure chambers are to be formed (Step IV). As described above, the etching
protective film 91 on the opposite face of the substrate 90 is etched away by hydrogen
fluoride so as to coincide of the shapes of the pressure chamber, a reservoir, and
an ink supply port, thereby forming the window 99 (Step V). The single-crystal silicon
substrate 90 is subjected to anisotropic etching with using an anisotropic etchant,
for example, an about 17% by weight aqueous solution of potassium hydroxide heated
to 80°C, so that the etched portion reaches the protective film 91 on the surface.
Thereafter, the etching protective film 91 of the piezoelectric film is etched away
by hydrogen fluoride (Step VI).
[0057] The thus formed driving portion has an electrostatic capacity of 5 nF per element.
As compared with an electrostatic capacity of about 10 nF obtained in the prior art,
the electrostatic capacity is reduced to about one half. Reliability evaluation tests
by means of long term printing were performed. In prior art recording heads, at 50,000,000
ink drop ejections, an ink ejection failure occurred in 10% of the recording heads.
By contrast, in recording heads according to the invention, the defective rate was
about 1% or less even at 2,000,000,000 ink ejections.
[0058] In the above, the embodiment in which the low-dielectric constant layer 118 is made
of titanium oxide has been described. Alternatively, the layer may be made of a material
which is suitable for forming a low-dielectric constant film, such as silicon, silicon
oxide, aluminum oxide, zirconium oxide or lead oxide. It is preferable to use a material
which contains an element which configures the piezoelectric film 117, in order to
enhance the adhesion strength exerted between films and prevent an unexpected reaction
from occurring. In the embodiment, the low-dielectric constant layer and the piezoelectric
film are simultaneously baked. Alternatively, they may be separately baked, or formed
without conducting the baking process or by depositing a low-dielectric constant material
on the surface of a piezoelectric film.
[0059] In the embodiment, the low-dielectric constant layer 111 is made of a material which
is lower in dielectric constant than the piezoelectric film. Alternatively, the layer
may be made of the same material as the piezoelectric film, the upper electrode 119
may be formed by sputtering platinum in the same manner as described above, and the
upper electrode and the lead portion may be then patterned. Also in the alternative,
the lead portion can be thicker than the region which functions as the piezoelectric
member, and hence it is apparent that the electrostatic capacity of the wiring region
can be reduced.
[0060] When the wiring region is formed by the same piezoelectric material as described
above, it is preferable in the view point of production to employ a configuration
in which a piezoelectric material layer of a uniform thickness suitable for a wiring
region and the region other than the wiring region is caused by etching or the like
to function as the piezoelectric film.
[0061] In the above, the embodiment in which the driving portion is directly formed on an
elastic plate which is integrated with the flow path substrate has been described.
Alternatively, the elastic film and the driving portion may be configured as separate
members and they may be then integrally fixed to each other by an adhesive agent.
These alternatives attain the same effects. Specifically, as shown in FIG. 19, a pressure
chamber 130 is formed in the form of a through hole on a flow path substrate 133 in
which the pressure chamber 130, an ink supply port 131, and a reservoir 132 are formed.
A nozzle plate 134 is liquid-tightly fixed to one face of the substrate. A pressure
film substrate 136 on which a driving portion 135 is formed and which is configured
as a separate member is liquid-tightly fixed to the other face of the substrate. In
the pressure film substrate 136, an elastic film 138 functioning also as a lower electrode,
a piezoelectric film 139, and an upper electrode 140 are formed on the surface of
a single-crystal silicon substrate by the same technique described above, and then
patterned so as to be formed as the driving portion 135. Thereafter, anisotropic etching
is conducted on the opposite face (in the figure, the lower face) of the single-crystal
silicon substrate and a recess 142 is formed so that a wall 141 is positioned between
the driving portions 135. According to the embodiment, the elastic film 138 can be
supported at various points by the wall 141, and hence crosstalk can be prevented
from occurring even when a partition wall 130a defining the pressure chamber 130 of
the flow path substrate 133 is made thin so that the arrangement pitch of the pressure
chambers 130 is small. Since the elastic film 138 having the driving portions 135
can be formed as a separate member, the pressure chamber can be configured by conducting
etching on the face of the flow path substrate 133 opposite to the side where a nozzle
opening 143 is opened, i.e., the face opposite to that used in the case where an elastic
film is integrated with a flow path substrate. Therefore, the pressure chamber 131
can be formed into a shape in which the dimension is gradually reduced in a direction
moving from the driving portion 135 toward the nozzle opening 143, so that ink pressurized
in the pressure chamber 130 is allowed to smoothly flow to the nozzle opening 143.
[0062] An ink jet recording head comprises: a nozzle plate 12, 53, 134 in which a plurality
of nozzle openings 10, 11, 52, 143 are formed, a flow path substrate comprising a
reservoir 5, 6, 21, 22, 23, 69, 132 to which ink is externally supplied, and a plurality
of pressure chambers 3, 4, 24, 25, 64, 100, 130 which are connected to said reservoir
5, 6, 21, 22, 23, 69, 132 via an ink supply port 26, 27, 28, 29, 68, 131 and which
respectively communicate with said nozzle openings 10, 11, 52, 143, an elastic film
43, 61, 73, 82, 138 which pressurizes ink in said pressure chambers 3, 4, 24, 25,
64, 100, 130, and driving means located at a position opposing said respective pressure
chamber 3, 4, 24, 25, 64, 100, 130 for causing said elastic film 43, 61, 73, 82, 138
to conduct flexural deformation, wherein said pressure chambers 3, 4, 24, 25, 64,
100, 130 are arranged in a single-crystal silicon substrate 40, 70, 90 of a (110)
lattice plane and along a 〈112〉 lattice orientation.
[0063] In this ink jet recording head said elastic film 43, 61, 73, 82, 138 is formed integrally
with one face of said single-crystal silicon substrate 40, 70, 90 by a film formation
method, and/or said driving means is formed as a piezoelectric element in a lamination
structure and integrally with said single-crystal silicon substrate 40, 70, 90 and/or
said piezoelectric element comprising: a first electrode film formed on a surface
of said elastic film 43, 61, 73, 82, 138, a piezoelectric film 13, 14, 44, 83, 96,
110, 117, 139 formed on said first electrode film, and a second electrode film formed
on said piezoelectric film 13, 14, 44, 83, 96, 110, 117, 139.
[0064] At least a part of said driving means has a region narrower than a width of said
pressure chamber 3, 4, 24, 25, 64, 100, 130.
[0065] The first electrode film serves also as said elastic film 43, 61, 73, 82, 138 and
has a thickness of 0.2 to 2.5 µm. The ink supply port 26, 27, 28, 29, 68, 131 is formed
at both ends in a longitudinal direction of said pressure chamber 3, 4, 24, 25, 64,
100, 130.
[0066] A method of producing an ink jet recording head comprises the steps of:
forming an etching protective film on a first and second face of a single-crystal
silicon substrate in which a lattice plane of a surface is (110);
forming a first electrode film on said first face of said single-crystal silicon substrate;
forming a piezoelectric film on a surface of said first electrode film;
forming a second electrode film on a surface of said piezoelectric film;
dividing at least said second electrode film and piezoelectric film in correspondence
with a shape of a pressure chamber;
a first patterning step of removing a part of said etching protective film from said
second face of said single-crystal silicon substrate, thereby forming a window;
a second patterning step of thinning said etching protective film in a region opposing
an ink supply port;
a first etching step of conducting anisotropic etching on said single-crystal silicon
substrate in accordance with said window formed in said first patterning step; and
a second etching step of removing said etching protective film which is thinned in
said second patterning step: and conducting anisotropic etching.
[0067] The anisotropic etching step forms first side walls of said pressure chamber in a
plane perpendicular to said lattice plane of said single-crystal silicon substrate
and forms second side walls in a (-11-1) plane.
[0068] Further, an ink jet recording head comprises: a nozzle plate 53 in which a plurality
of nozzle openings 52 are formed, a flow path substrate comprising a reservoir 21,
22, 23 to which ink is externally supplied, and a plurality of pressure chambers 24,
25 which are connected to said reservoir 21, 22, 23 via an ink supply port 26, 27,
28, 29 and which respectively communicate with said nozzle openings 52, an elastic
film 43 which pressurizes ink in said pressure chambers 24, 25, and driving means
located at a position opposing said respective pressure chamber 24, 25 for causing
said elastic film 43 to conduct flexural deformation, wherein said pressure chambers
24, 25 are arranged in a single-crystal silicon substrate 40 of a (110) lattice plane
and along a 〈112〉 lattice orientation, and a nozzle connecting portion 56 is formed
in a first region of said pressure chambers 24, 25, said nozzle connecting portion
56 opposing said nozzle openings 52, and said nozzle connecting portion 56 being wider
than a second region of said pressure chambers 24, 25.
[0069] The nozzle connecting portion 56 is formed at a position opposing an inclined face
at an end portion of said pressure chamber 24, 25.
[0070] Further, an ink jet recording head comprises: a nozzle plate 53 in which a plurality
of nozzle openings 52 are formed, a flow path substrate comprising a reservoir 21,
22, 23 to which ink is externally supplied, and a plurality of pressure chambers 24,
25, 64 which are connected to said reservoir 21, 22, 23 via an ink supply port 26,
27, 28, 29 and which respectively communicate with said nozzle openings 52, an elastic
film 43 which pressurizes ink in said pressure chambers 24, 25, 64, and driving means
located at a position opposing said respective pressure chamber 24, 25 for causing
said elastic film 43 to conduct flexural deformation, wherein said pressure chambers
24, 25, 64 are arranged in a single-crystal silicon substrate 40 of a (110) lattice
plane and along a 〈111〉 lattice orientation, said pressure chamber 24, 25, 64 is divided
by a center partition wall 60 elongating from said elastic film 43, into a plurality
of cells 64a, 64b communicating with each other at least in the vicinity of said nozzle
opening 52, said pressure chamber 24, 25, 64 communicates with one nozzle opening
52, and a part of said center partition wall 60 supports said nozzle plate 53.
[0071] A method of producing an ink jet recording head comprises:
a step of forming an etching protective film on a single-crystal silicon substrate
in which a lattice plane of a surface is (110);
a first patterning step of removing a part of said etching protective film on one
face of said single-crystal silicon substrate, thereby forming a window;
a second patterning step of thinning said etching protective film in a region opposing
a nozzle connecting portion and an ink supply port;
a first etching step of conducting anisotropic etching on said single-crystal silicon
substrate in accordance with said window formed in said first patterning step;
a second etching step of removing said etching protective film which is thinned in
said second patterning step; and conducting anisotropic etching.
[0072] The above anisotropic etching step forms a step in the center of a partition wall.
1. An ink jet recording head comprising:
a nozzle plate (53) in which a plurality of nozzle openings (52) are formed;
a flow path substrate (80) comprising a reservoir (21, 22, 23, 69) to which ink is
externally supplied, and a plurality of pressure chambers (24, 25; 64; 100) which
are connected to said reservoir (21, 22, 23; 69) via an ink supply port (26, 27, 28,
29; 68) and which respectively communicate with said nozzle openings (52);
an elastic film (73; 82) which pressurizes ink in said pressure chambers (24, 25;
64; 100); and
driving means located at a position opposing said respective pressure chambers (24,
25; 64; 100) for causing said elastic film (82) to conduct flexural deformation,
wherein said ink jet recording head further comprises on a surface of said elastic
film (73; 82), a lower electrode (92), and a piezoelectric film (96) formed in a region
opposing said respective pressure chamber (24, 25; 64; 100), and a different composition
film (97) formed in a wiring region (95) for supplying a driving signal to said piezoelectric
film (96), said different composition film (97) having a dielectric constant and piezoelectric
properties which are lower than those of said piezoelectric film (96), an upper electrode
(98) formed on a surface of said piezoelectric film (96), and a lead pattern which
is formed on a surface of said different composition film (97) and connected to said
upper electrode (98).
2. The ink jet recording head according to claim 1, wherein said piezoelectric film (96)
and said different composition film (97) contain an identical element, and are different
in composition.
3. The ink jet recording head according to claim 1 or 2, wherein said piezoelectric film
(96) is Pb
CTi
AZr
BO
3 (where A, B and C are numerals,
, 0.5 ≤ A ≤ 0.6, and 0.85 ≤ C ≤ 1.10).
4. The ink jet recording head according to one of claims 1 to 3, wherein said different
composition film (97) is Pb
CTi
AZr
BO
3 (where A, B and C are numerals,
, and A ≤ 0.5 or 0.6 ≤ A).
5. The ink jet recording head according to one of claims 1 to 3, wherein said different
composition film (97) is Pb
CTi
AZr
BO
3 (where A, B and C are numerals,
, and C ≤ 0.85 or 1.10 ≤ C).
6. The ink jet rcording head according to one of claims 1 to 5, wherein said piezoelectric
film (96) contains Pb(Mg1/3Nb2/3O3).
7. The ink jet recording head according to one of claims 1 to 6, wherein said wiring
region (95) is formed in a region which does not oppose said reservoir (21, 22, 23).
8. A method of producing an ink jet recording head, comprising the steps of:
forming a piezoelectric film by a piezoelectric film precursor;
forming a film containing a material for a different composition film in a wiring
region of said piezoelectric film precursor;
baking said film; and patterning said film into a shape corresponding to a pressure
chamber and a lead pattern.
9. An ink jet recording head comprising:
a nozzle plate (53) in which a plurality of nozzle openings (52) are formed;
a flow path substrate (80) comprising a reservoir (21, 22, 23; 69) to which ink is
externally supplied, and a plurality of pressure chambers (24, 25; 64; 100) which
are connected to said reservoir (21, 22, 23; 69) via an ink supply port (26, 27, 28,
29; 68) and which respectively communicate with said nozzle openings (52);
an elastic film (73; 82) which pressurizes ink in said pressure chambers (24, 25;
64; 100); and
driving means located at a position opposing said respective pressure chamber (24,
25; 64; 100) for causing said elastic film (73; 82) to conduct flexural deformation,
wherein a lower electrode (92), and a piezoelectric film (96) are laminated on a surface
of said elastic film (82), and a low-dielectric constant film (111) which is lower
in dielectric constant than said piezoelectric film (96), and an upper electrode (98)
are laminated in a wiring region (95) for supplying a driving signal to said piezoelectric
film (96).
10. The ink jet recording head according to claim 9, wherein said low-dielectric constant
film (111) is made of an oxide of a metal element which configures said piezoelectric
film (96).
11. The ink jet recording head according to claim 9 or 10, wherein said piezoelectric
film (96) is PbTi
AZr
B(Mg
1/3Nb
2/3)
CO
3+ePbO (where A, B, C and e are numerals,
, 0.35 ≤ A ≤ 0.55, 0.25 ≤ B ≤ 0.55, 0.1 ≤ C ≤ 0.4, and 0 ≤ e ≤ 0.3).
12. The ink jet recording head according to one of claims 9 to 11 wherein said low-dielectric
constant film (111) is made of at least one selected from the group consisting of
lead oxide, titanium oxide, and zirconium oxide.
13. A method of producing an ink jet recording head comprising the steps of:
forming a piezoelectric film by a piezoelectric film precursor;
forming a low-dielectric constant film in a wiring region of said piezoelectric film
precursor;
baking one of said piezoelectric film and said low-dielectric constant film; and
patterning said piezoelectric film into a shape corresponding to a pressure chamber
and a lead pattern.
14. An ink jet recording head comprising:
a nozzle plate (53) in which a plurality of nozzle openings (52) are formed;
a flow path substrate (80) comprising a reservoir (21, 22, 23; 69) to which ink is
externally supplied, and a plurality of pressure chambers (24, 25; 64; 100) which
are connected to said reservoir (21, 22, 23; 69) via an ink supply port (26, 27, 28,
29; 68) and which respectively communicate with said nozzle openings (52);
an elastic film (73; 82) which pressurizes ink in said pressure chambers (24, 25;
64; 100); and
driving means located at a position opposing said respective pressure chamber (24,
25; 64; 100) for causing said elastic film (73; 82) to conduct flexural deformation,
wherein a lower electrode (92), a piezoelectric film (96), a wiring region (95) in
which a piezoelectric material having a composition which is the same as the composition
of said piezoelectric film (96), and an upper electrode (98) patterned by etching
are laminated on a surface of said elastic film (73; 82).
15. A method of producing an ink jet recording head comprising the steps of:
forming a piezoelectric film at a thickness suitable for a wiring region;
thinning said piezoelectric film to a thickness suitable for piezoelectric vibration;
and
patterning said piezoelectric film to a shape corresponding
to a pressure chamber and a lead pattern.